This invention relates to particle study devices and more specifically to a device for ejecting a specific amount of particulate matter into a diluent stream leading to a sensing zone.
In the field of particle analysis and study, particles to be counted and sized are passed through a sensing zone in a particle study device such as a Coulter type particle study device which operates on the Coulter sensing principle disclosed in U.S. Pat. No. 2,656,508, issued Oct. 20, 1953 to Wallace H. Coulter.
In a Coulter type particle study device an electrode extends into an electrolyte on each side of an insulating wall. The insulating wall has a minute aperture formed therein, commonly referred to as a Coulter aperture. An electrical excitation is applied causing electric current to flow between the electrodes through the Coulter aperture. According to the Coulter principle, particles passing through the aperture from one body of electrolyte to the other body of electrolyte will change the impedance of the electrolyte contained within the aperture. This change in impedance coacting with the electrical excitation causes a particle pulse to be developed. The particle pulse is coupled to a particle analyzer in the particle study device in order to provide a particle count and in order to provide an indication of the particle size or volume.
Heretofore, it has been common practice to employ the fluid electrolyte for diluting a sample of particles to be studied. The dilution is necessary because the particles to be studied most often exist in a very high concentration. The amount of particles in a small sample is most often so great that a small quantity, passing through the sensing zone, would pass through so quickly that they could not be accurately counted and sized. Furthermore, it is generally only necessary to study or analyze a very small amount of particulate matter in order to be able to ascertain the number in a specific volume and the size of the particulate matter. For example, blood generally has approximately 5,000,000 cells per cubic millimeter, and it is only necessary to study or analyze one hundredth of that amount, namely, a volume of 0.01 cubic millimeters.
The dilution of particulate matter to be studied has most commonly been performed by trained technicians. This process of diluting a specific amount of particulate matter in a specific volume of diluent was time consuming and had to be performed in an extremely careful fashion in order to provide an accurate count. This time consuming, tedious task prevented the trained technician from engaging in other, more profitable activities.
Recently, an ejecting mechanism has been developed, such as is described in the above mentioned incorporated by reference patent application, which ejects a predetermined amount of particulate matter into an electrolyte diluent leading to the sensing zone in the particle study device. This ejecting mechanism, although eliminating the necessity for precisely diluting a sample of particulate matter to be studied, has the disadvantage that it must first be manually loaded with a sample of particulate matter via an input port, then inserted into the particle study device and operated for ejecting a portion of the particles. After operation, the ejecting mechanism must again be removed, cleaned of remaining sample and manually refilled. This procedure, although it eliminates the precise dilution process previously required, is still unnecessarily time consuming and tedious.